Greetings. I have an old bike frame that I've been riding with a hodgepodge of new parts, and the other day I came across a serial number while cleaning it. I've checked out quite a few vintage biike websites trying to figure out what this thing is, but so far I'm no closer to IDing it than I was last weekend. There's no brands anywhere, and the frame has been stripped of lugs etc. I am hoping the style of serial number could tip someone off.

It's a fairly typical Middleweight "cruiser" type. Fairly long frame, curved horizontal bars.

The serial number are as follows:

503.45 12221
3071408

The second number is a bit larger than the first.

I will post some pics as soon as I can get some taken.

Vincent

Nope, the serial number is not enough to go by.
Have a look at the middleweights in our Picture Database and you may see your frame.

Vin - Menotomy Vintage Bicycles, Inc.
https://OldRoads.com